A bichromophoric dyad composed of a Prodan-derived moiety and a BODIPY dye was prepared, photophysically characterized, and tested for multiphoton fluorescence microscopy of N13 microglial cells. The dyad shows highly efficient energy transfer, independent on the solvent polarity of the medium. However, in polar media photoinduced electron transfer is a competitive pathway. The Prodan-derived chromophore shows significant two-photon absorption. Hence, it can be used a two-photon-absorbing antenna for the sensitization of BODIPY fluorescence.

Polycyclic aromatic hydrocarbon chromophores that show an ideal bipartition between fluorescence and singlet oxygen production have been developed.

An aminonaphthalimide-squaraine non-conjugated system was designed and synthetized with the purpose of preparing fluorescent molecule in the 650-700 nm region that could operate via energy transfer (ET) between covalently linked naphthalimide and squaraine chromophores. The photophysical properties of the new fluorescent system were explored with the aim of understanding the ET in one- and two-photon excitation modes. The spectroscopic techniques employed in the characterization includes; absorption, fluorescence, quantum yields and fluorescence lifetime measurements in different solvents. The effect of polarity of solvents on efficiencies of ET were evaluated using one- and two-photon excited fluorescence. The optical behavior of the non-conjugated system was compared with its individual squaraine and naphthalimide moieties. The two-photon absorption (TPA) spectrum of the molecule was obtained between 750 and 1040 nm, with the largest two-photon cross section (delta(TPA))above 4200 GM. Finally, the applicability of the molecule for fluorescence imaging in the one- and two-photon excitation mode was demonstrated in N13 Microglial cells. The in vitro and in vivo confocal microscopy studies indicated that the non-conjugated system efficiently accumulated in the cytoplasm suggesting it could be utilized as a subcellular probe. (C) 2021 The Authors. Published by Elsevier B.V.

The preparation and characterization of new functional materials for sensing have an important role in clinical diagnosis. Monitoring the surface functionalization of functional material is crucial because the final sensing properties are affected by how the (bio)molecules are immobilized on the surface of solid supports. Here, a new approach for the preparation of functional materials for biomedical diagnosis was developed. This method employs a fluorescent dye comprising 4-amino-1,8-naphthalimide with two orthogonal functional groups suitable for click chemistry. The orthogonal reactivity of these groups allows the sequential functionalization of the fluorophore, firstly with (bio)molecules, and then binding of the (bio)molecule-naphthalimide macrostructure onto the surface of a solid support. The fluorescent properties confirm the immobilization of the (bio)molecule on the surface of the solid support, without requiring other indirect methods to verify the immobilization. These functional materials were tested successfully with sera of patients, thus proving their potential application for allergic drug diagnosis.

Over the past two decades, integrated photonic sensors have been of major interest to the optical biosensor community due to their capability to detect low concentrations of molecules with label-free operation. Among these, interferometric sensors can be read-out with simple, fixed-wavelength laser sources and offer excellent detection limits but can suffer from sensitivity fading when not tuned to their quadrature point. Recently, coherently detected sensors were demonstrated as an attractive alternative to overcome this limitation. Here we show, for the first time, to the best of our knowledge, that this coherent scheme provides sub-nanogram per milliliter limits of detection in C-reactive protein immunoassays and that quasi-balanced optical arm lengths enable operation with inexpensive Fabry-Perot-type lasers sources at telecom wavelengths.

Boronic acid-derived salicylidenehydrazone complex (BASHY) dyes with a polymethine backbone were designed to yield efficient red-emitting and two-photon absorbing fluorophores that can be used as markers for astrocytes. The dyes are chemically stable in aqueous solution and do not undergo photodecomposition. Their photophysical properties can be electronically fine-tuned and thereby adapted to potentially different imaging situations and requirements.

Antonio J. Ruiz-Sanchez, Daniel Collado, Cristobalina Mayorga, Maria J. Torres, Ezequiel PerezInestrosa Departamento de Química Orgánica, Universidad de Málaga—IBIMA, 29071 Málaga, Spain Andalusian Centre for Nanomedicine and Biotechnology-BIONAND, Parque Tecnológico de Andalucía, 29590 Málaga, Spain Allergy Unit, IBIMA—Regional University Hospital of Málaga—UMA, 29009 Málaga, Spain ajruizs@uma.es

Four-coordinate N,C-chelate organoboron dyes with alkynyl spacers were synthesized by Heck alkynylation. These dyes are pi-extended analogues of the recently reported class of four-coordinate borylated arylisoquinolines (BAI). Depending on the electron-donor substitution, they feature an intramolecular charge-transfer (ICT) character in the excited state. This translates into pronounced apparent Stokes shifts (up to 8500 cm(-1)) and a solvatofluorochromic behavior. In general, the observed emission quantum yields are high in nonpolar media (Phi(F) ca. 0.5-0.6). For the dye with the most pronounced ICT rather high emission quantum yields (Phi(F) ca. 0.4) are observed for emissions with maxima longer than 600 nm in solvents of moderate polarity. The pi-extended dyes show interesting two-photon absorption (TPA) properties, maintaining high cross sections (up to 60 GM) in the near-infrared wavelength window (>900 nm). One of the dyes was designed as dimeric chromophore, integrating the acceptor-pi-acceptor (A-pi-A) format. This alternative design showed no ICT behavior but led to the observation of high two-photon-absorption (TPA) cross sections (ca. 220 GM at 700 nm). All investigated dyes show pronounced photostability, providing added value to this structural and photofunctional extension of the BAI dye platform.

Cell recognition, adhesion, and internalization are involved in infectious, reproductive, and inflammatory processes and are generally mediated by interactions between molecules located in the cell membrane and the extracellular matrix. These processes can decrease proliferation rates and they are well known for bacteria, fungi, and animals, but there is a lack of knowledge regarding autotrophic cells. Carbohydrates and proteins (e.g., lectins) are important molecules for cell interactions and information about these molecules is essential to better understand many biological phenomena in uni- or multicellular organisms. Most studies focus on the identification of the carbohydrates present on the cell surface by using labeled lectins. Alternatively, here we present a pioneer research performed by using three different labeled carbohydrates in a multivalent presentation (glycodendrons) to detect the presence of carbohydrate receptors (e.g., lectins) on cell surfaces of 12 algal species. The goal of this study was to detect some specificity in these molecular interactions, but in a reverse way in comparison to that commonly described in the literature. We tested trivalent molecules containing residuals of D-mannose, L-fucose, or N-acetyl-galactosamine to identify their bindings with the corresponding lectins expressed on cell surfaces. We envisage that our new approach could be an alternative tool for taxonomic and physiological studies on microalgae or even on other groups of organisms. Based on our results, the receptors found in the cell surface of the algal species tend to differ in composition, quantity, and distribution. The differences were mainly species-specific, since no patterns were identified at higher taxonomic level. Moreover, like lectins, labeled carbohydrates were proved to be a reliable tool for the study of cell surface composition.

Cellular adhesion and differentiation is conditioned by the nanoscale disposition of the extracellular matrix (ECM) components, with local concentrations having a major effect. Here we present a method to obtain large-scale uneven nanopatterns of arginine-glycine-aspartic acid (RGD)-functionalized dendrimers that permit the nanoscale control of local RGD surface density. Nanopatterns are formed by surface adsorption of dendrimers from solutions at different initial concentrations and are characterized by water contact angle (CA), X-ray photoelectron spectroscopy (XPS), and scanning probe microscopy techniques such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The local surface density of RGD is measured using AFM images by means of probability contour maps of minimum interparticle distances and then correlated with cell adhesion response and differentiation. The nanopatterning method presented here is a simple procedure that can be scaled up in a straightforward manner to large surface areas. It is thus fully compatible with cell culture protocols and can be applied to other ligands that exert concentration-dependent effects on cells.

Arginine-glycine-aspartic acid (RGD) dendrimer-based nanopatterns on poly(L-lactic acid) were used as bioactive substrates to evaluate the impact of the RGD local surface density on the chondrogenic induction of adult human mesenchymal stem cells. During chondrogenic commitment, active extracellular matrix (ECM) remodeling takes place, playing an instructive role in the differentiation process. Although three-dimensional environments such as pellet or micromass cultures are commonly used for in vitro chondrogenic differentiation, these cultures are rather limited with respect to their ability to interrogate cells in cell–ECM interactions. In the present study, the nanopatterns of the tunable RGD surface density were obtained as a function of the initial dendrimer concentration. The local RGD surface density was quantified through probability contour plots for the minimum interparticle distance, constructed from the corresponding atomic force microscopy images, and correlated with the cell adhesion and differentiation response. The results revealed that the local RGD surface density at the nanoscale acts as a regulator of chondrogenic commitment, and that intermediate adhesiveness of cells to the substrates favors mesenchymal cell condensation and early chondrogenic differentiation.

A series of boronic acid derived salicylidenehydrazone (BASHY) complexes was prepared and photophysically characterized. The dye platform can be modified by (a) electronic tuning along the cyanine-type axis via modification of the donor-acceptor pair and (b) functional tuning via the boronic acid residue. On the one hand, approach (a) allows the control of photophysical parameters such as Stokes shift, emission color, and two-photon-absorption (2PA) cross section. The resulting dyes show emission light-up behavior in nonpolar media and are characterized by high fluorescence quantum yields (ca. 0.5-0.7) and brightness (ca. 35000-40000 M-1 cm-1). Moreover, the 2PA cross sections reach values in the order of 200-300 GM. On the other hand, the variation of the dye structure through the boronic acid derived moiety (approach (b)) enables the functionalization of the BASHY platform for a broad spectrum of potential applications, ranging from biorelevant contexts to optoelectronic materials. Importantly, this functionalization is generally electronically orthogonal with respect to the dye's photophysical properties, which are only determined by the electronic structure of the cyanine-type backbone (approach (a)). Rare exceptions to this generalization are the presence of redox-active residues (such a triphenylamine or pyrene). Finally, the advantageous photophysics is complemented by a significant photostability.

Bis(dioxaborine) dyes of the A-pi-A format (A: acceptor, pi: conjugated bridge) were prepared and photophysically characterized. The best performing dyes feature (a) visible-light absorption (>400 nm), (b) high molar absorption coefficients (up to 70000 (-1)(M) cm(-1)), (c) Stokes shifts in the range of ca. 2500-5800 cm(-1), and (d) strong fluorescence emission with quantum yields of up to 0.74. This yields very bright-emitting dyes for one-photon excitation. However, the most intriguing feature of the dyes is their strong two-photon absorption. This was achieved by means of increased pi-conjugation in the phenylene or phenylene-thiophene bridges through the variation of the conjugation length and rigidity. This provided two-photon absorption cross sections of up to 2800 GM (1 Goeppert-Mayer (GM)= 10- 50 cm(4)sphoton(-1)). Considering the mentioned high fluorescence quantum yields, exceptionally bright-emitting A-pi-A two-photon absorbing dyes with low molecular mass are obtained. Time-dependent density-functional theory calculations corroborated the experimental results.

Seven tetracoordinate organoboron fluorophores with heterobiaryl N,O- or N,N-chelate ligands were prepared and photophysically characterized (in toluene). The electronic variation of the heteroaromatic moiety provided a means for the fine-tuning of the UV/vis absorption and emission spectra. In the most interesting cases, the spectra were red-shifted to maximum absorbance at wavelengths longer than 500 nm and emission maxima between 620 and 660 nm. The pronounced intramolecular charge-transfer character of the dyes yielded large Stokes shifts (3500-5100 cm-1), while maintaining appreciable fluorescence quantum yields of up to 0.2 for emission maxima longer than 600 nm. The lipophilic character of the dyes enabled their application as stains of vesicle substructures in confocal fluorescence microscopy imaging.